Conventional beds generally include a mattress supported upon a box spring, a wooden bed frame or both. Box springs are generally designed to have the outward appearance of a mattress, being covered in quilted fabric and cushioning for example. Generally, box springs have a wooden rectangular frame supporting an array of springs to provide firm support for the mattress.
Bed frames may simply support a mattress on boards spanning between side rails of the frame, or may accomodate a box spring. Bed frames conventionally have a head board, a foot board and two side rails, and are constructed to be easily assembled and disassembled.
A box spring is typically constructed in one piece of the same dimensions as the mattress it supports. Legs are provided with embedded threaded metal rods to be screwed into threaded inserts in the bottom of the box spring frame, when the box spring is used without a bed frame. In use, the legs often work loose destabilizing the box spring, or damaging the wooden box spring frame. As a result such screw-in box spring legs are totally unsuitable for use with heavy hybrid waterbed mattresses.
Alternatively, if the box spring does not have its own legs, a relatively expensive nine-leg metal platform is used under the box spring. The metal frame represents an additional expense, however the increased strength and stability of a metal frame, especially when casters are used, are necessary and justifiable in many cases. The metal platform results in an inferior unsightly appearance. The platform's metal rails may protrude beyond the bed creating a safety hazard and exposing bed linens to possible damage. However due to the increased load bearing capacity of metal frames, they are used extensively to support waterbeds and a high percentage of conventional spring beds.
A conventional box spring, due to its stiff wooden frame, is often heavy and awkward to handle, especially the larger "king size" or "queen size" variety. Moving such box springs, in apartment elevators and around corners into bedrooms for example, is often difficult and exposes the box spring and doorways to potential damage.
The use of waterbed mattresses dictate that bed frames and box springs have greatly enhanced load bearing capacity due to the weight of the water enveloped in the waterbed bladders. Hybrid waterbed mattresses are increasingly used in which water filled bladders are embedded in foam cushioning encased in an external quilted fabric. The hybrid waterbed mattress therefore has the outward appearance and many functional characteristics of a conventional spring or foam mattress, but is of much greater weight. Hybrid waterbed mattresses are constructed with outer dimensions identical to conventional spring mattresses, which contributes much to their marketplace acceptance.
Waterbeds, including hybrid types, suffer from the disadvantage that, due to increase strength requirements, the waterbed frames are necessarily heavier than conventional bed frames. Waterbed frames appear bulky and are different in appearance from conentional bed frames which impedes their marketplace acceptance.
Due to their weight, hybrid waterbeds commonly use the nine-leg metal platform described above. The metal platform and legs provide the required support in comparison to the inadequate screw-in legs of a wooden frame box spring.